Helically wound fin tube coils are frequently used for outdoor heat exchangers in air conditioning units including cooling-only units and heat pumps. The wound coils provide an adequate heat exchange surface for the outdoor heat exchanger in an acceptable size, and can be relatively inexpensively manufactured, particularly for residential size units. The outdoor heat exchanger of the air conditioner frequently includes a plurality of circuits, and the coil may be wound in generally rectangular or annular shapes. The coil is disposed on a frame or base, with a guard disposed there around and a cover or grill disposed on the top thereof for protection, the guard, cover and base essentially defining the perimeter of the outdoor unit. Arranged within the space defined by the coil of conventional units are the compressor, outdoor fan, inlet and outlet manifolds, expansion valves, check valves, filters driers and, in a heat pump, a reversing valve, with appropriate interconnecting refrigerant lines therebetween. A compact outdoor unit is thus provided, requiring only hookup to the indoor heat exchanger and an electric power source. A typical coil is shown in U.S. Pat. No. 4,535,838 to Gray et al. This patent is commonly assigned with the present invention and incorporated by reference herein.
Typical manufacturing methods for such coils include winding the entire coil, either vertically or horizontally, from a continuous length of fin tubing, and thereafter determining in which wraps inlets and outlets for adjacent circuits should be made.
Virtually all helically wound fin tube coils are formed around a mandrel. A number of devices have been designed to noncontinuously perform the helical winding operations. Such devices include a tube guide mounted on a lead screw for helically advancing the coil onto the mandrel as shown in U.S. Pat. No. 5,099,574 to Paulman et al. U.S. Pat. No. 4,085,488 to Hanert et al. discloses a geared, translating tube guide that is driven on wheels across a surface to advance the tube onto a mandrel. A rotating cylindrical feed device is disclosed in U.S. Pat. No. 4,077,116 to Cunningham et al. The cylindrical feeder that is disclosed is oriented transverse to the mandrel and rotation of the feeder through approximately one-third of a revolution advances the tube onto the mandrel.
Several additional patents are of interest in showing the state of the art. There is a series of patents to McManus and to McManus et al., all of which are assigned to the same assignee and include U.S. Pat. Nos. 4,619,024; 4,619,025; 4,633,941; and 4,770,241. These patents disclose winding of the tubing around two spaced-apart upright posts. The posts with the wound tube in place are then advanced around a stationary mandrel to generate a partially closed four sided heat exchanger.
It would be a decided advantage in the industry to be able to continuously form helically wound fin tube coils. Further, it would be advantageous if the device performing continuous helical formation were adaptable to form heat exchanger coils having a selected number of sides. The device should additionally reduce the floor space required to manufacture the heat exchanger and should also reduce the number of operations needed for forming multi-circuit heat exchangers. It would also be desirable to cut the helical coil at selected locations in order to form circuits having a desired length.